2026 Rankings

Highest Radon Risk ZIP Codes in California — 2026

Last updated: June 4, 2026

86 ZIP codes ranked by Radon Zone #1: ZIP 92101 (San Diego, CA) — Zone 1 (High)
Lead Violations Lowest Score Safest Flood Risk Energy Cost Radon PFAS Reliability EJ Index Homebuyer Risk CO & Gas Safest Gas Remediation Burden Unresolved Violations (by Utility) Water Equity (by Utility)

Out of 86 ZIP codes with data in California, these are the lowest-ranked areas for radon zone. See also: National ZIP Codes with Highest Radon Risk | All California Rankings

Statistic Value
ZIP codes ranked 86
Lowest value Zone 1 (High)
Median value Zone 1 (High)
State California

86 Lowest-Ranked ZIP Codes

Rank ZIP Code City State Radon Zone Safety Score
1 92101 San Diego CA Zone 1 (High) 35/100
2 91319 Newbury Park CA Zone 1 (High) 40/100
3 93042 Point Mugu Nawc CA Zone 1 (High) 40/100
4 93043 Port Hueneme Cbc Base CA Zone 1 (High) 40/100
5 91320 Newbury Park CA Zone 1 (High) 45/100
6 91377 Oak Park CA Zone 1 (High) 45/100
7 93001 Ventura CA Zone 1 (High) 48/100
8 93023 Ojai CA Zone 1 (High) 52/100
9 93044 Port Hueneme CA Zone 1 (High) 53/100
10 93067 Summerland CA Zone 1 (High) 53/100
11 93108 Santa Barbara CA Zone 1 (High) 53/100
12 93429 Casmalia CA Zone 1 (High) 53/100
13 93024 Ojai CA Zone 1 (High) 56/100
14 93035 Oxnard CA Zone 1 (High) 56/100
15 93065 Simi Valley CA Zone 1 (High) 56/100
16 93117 Goleta CA Zone 1 (High) 56/100
17 93002 Ventura CA Zone 1 (High) 57/100
18 93005 Ventura CA Zone 1 (High) 57/100
19 93006 Ventura CA Zone 1 (High) 57/100
20 93007 Ventura CA Zone 1 (High) 57/100
21 93009 Ventura CA Zone 1 (High) 57/100
22 93003 Ventura CA Zone 1 (High) 58/100
23 93101 Santa Barbara CA Zone 1 (High) 58/100
24 93103 Santa Barbara CA Zone 1 (High) 58/100
25 93105 Santa Barbara CA Zone 1 (High) 58/100
26 93022 Oak View CA Zone 1 (High) 59/100
27 93013 Carpinteria CA Zone 1 (High) 60/100
28 93041 Port Hueneme CA Zone 1 (High) 60/100
29 93060 Santa Paula CA Zone 1 (High) 60/100
30 93010 Camarillo CA Zone 1 (High) 61/100
31 93012 Camarillo CA Zone 1 (High) 61/100
32 93015 Fillmore CA Zone 1 (High) 61/100
33 93030 Oxnard CA Zone 1 (High) 61/100
34 93032 Oxnard CA Zone 1 (High) 61/100
35 93034 Oxnard CA Zone 1 (High) 61/100
36 93036 Oxnard CA Zone 1 (High) 61/100
37 93063 Simi Valley CA Zone 1 (High) 61/100
38 93116 Goleta CA Zone 1 (High) 61/100
39 93118 Goleta CA Zone 1 (High) 61/100
40 93199 Goleta CA Zone 1 (High) 61/100
41 93454 Santa Maria CA Zone 1 (High) 61/100
42 93463 Solvang CA Zone 1 (High) 61/100
43 93464 Solvang CA Zone 1 (High) 61/100
44 93062 Simi Valley CA Zone 1 (High) 62/100
45 93093 Simi Valley CA Zone 1 (High) 62/100
46 93094 Simi Valley CA Zone 1 (High) 62/100
47 93099 Simi Valley CA Zone 1 (High) 62/100
48 93427 Buellton CA Zone 1 (High) 62/100
49 93434 Guadalupe CA Zone 1 (High) 62/100
50 93456 Santa Maria CA Zone 1 (High) 62/100
51 93457 Santa Maria CA Zone 1 (High) 62/100
52 93004 Ventura CA Zone 1 (High) 63/100
53 93109 Santa Barbara CA Zone 1 (High) 63/100
54 93110 Santa Barbara CA Zone 1 (High) 63/100
55 91361 Westlake Village CA Zone 1 (High) 64/100
56 93106 Santa Barbara CA Zone 1 (High) 64/100
57 93107 Santa Barbara CA Zone 1 (High) 64/100
58 93120 Santa Barbara CA Zone 1 (High) 64/100
59 93121 Santa Barbara CA Zone 1 (High) 64/100
60 93130 Santa Barbara CA Zone 1 (High) 64/100
61 93140 Santa Barbara CA Zone 1 (High) 64/100
62 93150 Santa Barbara CA Zone 1 (High) 64/100
63 93160 Santa Barbara CA Zone 1 (High) 64/100
64 93190 Santa Barbara CA Zone 1 (High) 64/100
65 91360 Thousand Oaks CA Zone 1 (High) 65/100
66 91362 Thousand Oaks CA Zone 1 (High) 65/100
67 93441 Los Olivos CA Zone 1 (High) 65/100
68 93460 Santa Ynez CA Zone 1 (High) 65/100
69 91358 Thousand Oaks CA Zone 1 (High) 66/100
70 93011 Camarillo CA Zone 1 (High) 66/100
71 93016 Fillmore CA Zone 1 (High) 66/100
72 93020 Moorpark CA Zone 1 (High) 66/100
73 93031 Oxnard CA Zone 1 (High) 66/100
74 93033 Oxnard CA Zone 1 (High) 66/100
75 93061 Santa Paula CA Zone 1 (High) 66/100
76 93437 Lompoc CA Zone 1 (High) 66/100
77 93438 Lompoc CA Zone 1 (High) 66/100
78 93455 Santa Maria CA Zone 1 (High) 66/100
79 93458 Santa Maria CA Zone 1 (High) 66/100
80 93102 Santa Barbara CA Zone 1 (High) 68/100
81 93111 Santa Barbara CA Zone 1 (High) 68/100
82 93254 New Cuyama CA Zone 1 (High) 69/100
83 93014 Carpinteria CA Zone 1 (High) 70/100
84 93021 Moorpark CA Zone 1 (High) 70/100
85 93436 Lompoc CA Zone 1 (High) 70/100
86 93440 Los Alamos CA Zone 1 (High) 70/100

Methodology

Radon rankings are based on EPA county-level radon zone classifications. Zone 1 (highest risk) has predicted average indoor radon levels above 4 pCi/L — the EPA action level. Zone 2 is moderate (2-4 pCi/L) and Zone 3 is low (below 2 pCi/L). Within Zone 1, ZIP codes are sub-ranked by Home Safety Score to prioritize areas with compounding risk factors.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-06-04.

Frequently Asked Questions

What is EPA Radon Zone 1?

Zone 1 is the EPA highest-risk classification, meaning the county has predicted average indoor radon levels above 4 pCi/L — the level at which the EPA recommends mitigation. Radon causes about 21,000 lung cancer deaths per year in the U.S.

Should I test for radon?

The EPA recommends testing all homes regardless of radon zone. A DIY test kit costs $15-40. Professional testing costs $150-250. If levels exceed 4 pCi/L, mitigation systems ($800-2,500) can reduce radon by up to 99%.

Explore More Rankings

How this ranking is calculated, data sources, and limitations: Rankings Methodology →

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Disclaimer: Rankings are based on EPA, FEMA, and federal agency data. They reflect historical patterns and risk indicators, not necessarily current conditions. For the most current information, contact your local water utility or request a Consumer Confidence Report.

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